Visual function testing device

ABSTRACT

A visual function testing device includes: a visual target image presentation unit that presents a visual target image; a visual target image rendering unit that renders the visual target image to be presented on the visual target image presentation unit; a visual function test item selection unit that selects a visual function test item; a visual target image generation unit that generates a visual target image corresponding to the test item selected by the visual function test item selection unit; a viewpoint distance input unit that inputs a distance between the visual target image presentation unit and a viewpoint of an observer; and a visual angle input unit that inputs an angle to be made by the visual target image and the viewpoint of the observer. Based on the viewpoint distance and the visual angle, a display size and display position of a visual target image are calculated.

This application is a Continuation of U.S. patent application Ser. No.13/656,476, filed Oct. 19, 2012, which is based on InternationalApplication No. PCT/JP2011/059370, filed Apr. 15, 2011, claiming theforeign priority of Japanese Patent Application No. 2010-097833, filedApr. 21, 2010, the contents each of which are incorporated herein byreference.

TECHNICAL FIELD

The present disclosure relates to a visual function testing device thatperforms a plurality of visual function tests by itself.

BACKGROUND

Heretofore, visual function testing devices for testing a variety ofvisual functions have been known. In visual function tests in theophthalmic treatment, there are many test items. As the test itemsconcerned, there are visual acuity and field tests, a binocular visiontest, an eye position test, and the like. The visual function testingdevices for the variety of visual function tests as described above areconfigured according to specifications specialized for test contents ofthe respective items such as the visual acuity and the visual field, andaccordingly, there is not a visual function testing device capable oftesting the visual acuity, the visual field and the binocular vision byitself.

As the visual function testing devices, there are known visual functiontesting devices, each of which is capable of performing two items of thevisual function tests as described in Patent Literature 1 and PatentLiterature 2, which are described below.

The visual function testing device described in Patent Literature 1(Japanese Patent No. 3168056) has a function to present visual targetsindividually to left and right eyes by a dichoptic method using anoptical system, a polarization filter, and a red/green filter, and inthe same tester, uses such a visual target for the visual acuity testand such a visual target for the binocular vision test. In such a way,the visual function testing device of Patent Literature 1 can performtwo visual function tests, which are the visual acuity test and thebinocular vision test, by itself.

The visual function testing device described in Patent Literature 2(Japanese Patent Laid-Open Publication No. 2003-93344) is a deviceconfigured in such a manner that a liquid crystal display for the visualacuity test is arranged on a center thereof, and that a light source forthe visual field test, which is composed of a large number of LEDs, isarranged on a periphery of the liquid crystal display. In such a way,the visual function testing device of Patent Literature 2 can performtwo visual function tests, which are the visual acuity test and thevisual field test.

SUMMARY Technical Problem

However, with regard to the visual function testers using theabove-mentioned technology, there are instruments individually dedicatedfor the test items, and there is not a visual function testing devicecapable of testing more than two visual functions such as the visualacuity, the visual field, stereopsis, the binocular vision and the eyeposition.

Moreover, in the current visual acuity tester and visual field tester, avisual field of one eye is blocked by using an occluder and the like,and the tests are performed for each eye.

Moreover, since the current binocular vision tester realizes dichopticviewing by means of a structure of looking into a lens barrel, thevisual field is restricted, and accordingly, is narrowed. As describedabove, the current visual function testers block the visual field by theoccluder and restrict the visual field by the lens barrel, and therebyimplement the visual function tests in a state where visual performanceis different from a daily one.

It is one of the objectives of the present disclosure to provide avisual function testing device for performing the plurality of visualfunction tests by itself in a state where both eyes are opened and astate where visual performance is close to the daily one withoutrestricting the visual field.

Solution to Problem

A visual function testing device according to a first example of thepresent disclosure is a visual function testing device for testing aplurality of visual functions. The visual function resting deviceincludes a visual target image presenting unit for presenting a visualtarget image; a visual target image rendering unit for rendering thevisual target image to be presented on the visual target imagepresenting unit; a visual function test item selecting unit forselecting an item of a visual function test; a visual target imagegenerating unit for generating a visual target image corresponding tothe item of the test, the item being selected by the visual functiontest item selecting unit; a viewpoint distance inputting unit forinputting a distance between the visual target image presenting unit anda viewpoint of an observer; and a visual angle inputting unit forinputting an angle to be made by the visual target image and theviewpoint of the observer. Based on a viewpoint distance inputted by theviewpoint distance inputting unit and on the visual angle inputted bythe visual angle inputting unit, the visual target image rendering unitcalculates a display size and display position of a visual target imagecorresponding to a visual acuity or visual field test selected by thevisual function test item selecting unit, and renders the visual targetimage with the calculated display size at the calculated displayposition.

In a second example of the present disclosure as the visual functiontesting device according to the first example, the visual target imagegenerating unit has a binocular visual target image generation functionto generate visual target images for each of a right eye and left eye ofa subject, the visual target image presenting unit presents dichopticvisual target images for the right and the left eye, respectively, thedichoptic visual target images being separated for the right eye and theleft eye from the binocular visual target images generated by the visualtarget image generating unit, the visual function testing device furtherincludes a visual target image selection presenting unit configured toselect display or non-display of a right visual target image for theright eye or a left visual target image for the left eye independentlywith each other, the right and left visual target images being to bepresented by the visual target image presenting unit, and the visualtarget image selection presenting unit displays a visual target imagecorresponding to the stereopsis test selected by the visual functiontest item selecting unit.

A third example of the present disclosure as the visual function testingdevice according to the second example further includes a visual targetimage operating unit for changing at least one of the display size ordisplay position of the visual target image by an operation of a user.In a case where a binocular vision test or an eye position test isselected by the visual function test item selecting unit, the visualtarget image rendering unit changes the visual target image to thedisplay size and the display position, which are calculated by thevisual target image rendering unit, in accordance with the display sizeor the display position of the visual target image changed by the visualtarget image operating unit.

In a fourth example of the present disclosure as the visual functiontesting device according to any one of the first to third examples, thevisual target image rendering unit has a visual target image adjustingunit for adjusting brightness, contrast, color and transparency of thevisual target image.

A fifth example of the present disclosure as the visual function testingdevice according to any one of the first to fourth examples furtherincludes: a viewing angle inputting unit for inputting a viewing anglefor use in the visual field test in a case where the visual field testis selected by the visual function test item selecting unit; and aviewpoint distance calculating unit for calculating a viewpoint distanceto be required for implementing the visual field test at the viewingangle inputted by the viewing angle inputting unit in a screen dimensionof the visual target image presenting unit.

A sixth example of the present disclosure as the visual function testingdevice according to any one of the first to fifth examples furtherincludes: a visual acuity inputting unit for inputting visual acuity foruse in the visual acuity test in a case where the visual acuity test isselected by the visual function test item selecting unit; and aviewpoint distance calculating unit for calculating a viewpoint distanceto be required for implementing the visual acuity test at the visualacuity inputted by the visual acuity inputting unit in a resolution ofthe visual target image presenting unit.

A seventh example of the present disclosure as the visual functiontesting device according to any one of the second to sixth examplesfurther includes: a parallax inputting unit for inputting a parallax foruse in the stereopsis test in a case where the stereopsis test isselected by the visual function test item selecting unit; and aviewpoint distance calculating unit for calculating a viewpoint distanceto be required for implementing the stereopsis test at the parallaxinputted by the parallax inputting unit in the resolution of the visualtarget image presenting unit.

An eighth example of the present disclosure as the visual functiontesting device according to any one of the first to seventh examplesfurther includes: a viewpoint distance measuring unit for measuring adistance between the visual target image presenting unit and theviewpoint of the observer. The measured viewpoint distance is inputtedto the viewpoint distance inputting unit.

A ninth example of the present disclosure as the visual function testingdevice according to any one of the second to eighth examples furtherincludes: a visual target image storing unit for storing the visualtarget image generated by the visual target image generating unit; adisplay setting storing unit for storing the display size and thedisplay position of the visual target image, which are calculated byusing the viewpoint position inputted by the viewpoint distanceinputting unit and using visual angle inputted by the visual angleinputting unit; a visual target image selection storing unit for storingthe display or non-display of the visual target image for each of theright eye and the left eye, the display or the non-display being set bythe visual target image selection presenting unit; and a display ordersetting unit for setting a display order of a plurality of the visualtarget images by using in combination plural pieces of informationstored in the respective storing unit, the visual target images beingstored in the visual target image storing unit. In accordance with thedisplay order set by the display order setting unit, the visual targetimages stored in the visual target image storing unit are called out,and are rendered by the visual target image rendering unit.

A tenth example of the present disclosure as the visual function testingdevice according to any one of the first to ninth examples furtherincludes: an output unit for outputting test results of the visualfunction tests selected by the visual function test item selecting unit.The test results corresponding to the respective test items areoutputted in a predetermined format.

Advantageous Effects

In accordance with the present technologies disclosed herein, thedisplay size and the display position of the visual target image arecalculated based on the inputted viewpoint distance and visual angle,and the visual target image is rendered. Accordingly, without blockingthe visual field or restricting the viewing field, the plurality ofvisual function tests can be performed by the same device in a statewhere both eyes are opened and a state where the visual performance isclose to the daily one in which the viewing field is not restricted.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view showing a relationship between a viewpointposition P and a presentation surface of a visual target imagepresentation unit in a visual function testing device to be shown as anembodiment of the present disclosure.

FIG. 2 is a block diagram showing a configuration example of a visualfunction testing device to be shown as a first embodiment.

FIGS. 3( a) to 3(d) are views showing examples of a shape of thepresentation surface of the visual target image presentation unit: FIG.3( a) is a flat type; FIG. 3( b) is an arch type; FIG. 3( c) is a dometype; and FIG. 3( d) is a multi-surface type.

FIGS. 4( a) to 4(c) are views showing visual target images to bepresented to the visual target image presentation unit: FIGS. 4( a),4(b) and 4(c) are explanatory views of sizes of a Landolt ring, aradiant, and a visual target image, respectively.

FIG. 5 is a side view explaining a size viewable at a visual angle θfrom the viewpoint position P on the visual target image presentationunit.

FIG. 6 is a perspective view explaining a display position of the visualtarget image on the visual target image presentation unit.

FIG. 7 is a perspective view explaining that the visual target image isarranged on grid lines on the visual target image presentation unit.

FIGS. 8( a) and 8(b) are top views explaining a screen center to be setwith respect to the viewpoint position: FIG. 8( a) is a case where thescreen center is set at a position directly confronted to the viewpointposition; and FIG. 8( b) is a case where the screen center is set at aposition directly confronted to a left eye.

FIG. 9 is a view showing a specific example of the Landolt ring.

FIG. 10 is a front view showing a state where the visual target image asthe radiant is arranged with respect to an origin on the grid lines ofthe visual target image presentation unit.

FIG. 11 is a block diagram showing a configuration example of a visualfunction testing device to be shown as a second embodiment.

FIG. 12 is a view showing an example of displaying a visual target imageprovided with a parallax.

FIG. 13 is a view explaining a distance corresponding to the parallax ata time of displaying the visual target image provided with the parallax.

FIG. 14 is a view explaining human sensory fusion, and is an explanatoryview about a capability of recognizing, as an image, those in which asame image is changed in size and presented to left and right eyes.

FIG. 15 is a view explaining the human sensory fusion, and is anexplanatory view about a capability of recognizing, as an image, thosein which a same image is changed in blur difference and presented to theleft and right eyes.

FIG. 16 is a block diagram showing a configuration example of a visualfunction testing device to be shown as a third embodiment.

FIG. 17 is a block diagram showing a configuration example of a visualfunction testing device to be shown as a fourth embodiment.

FIG. 18 is a block diagram showing a configuration example of a visualfunction testing device to be shown as a fifth embodiment.

FIG. 19 is a block diagram showing a configuration example of a visualfunction testing device to be shown as a sixth embodiment.

FIG. 20 is a block diagram showing a configuration example of a visualfunction testing device to be shown as a seventh embodiment.

FIG. 21 is a block diagram showing a configuration example of a visualfunction testing device to be shown as an eighth embodiment.

FIG. 22 is a block diagram showing a configuration example of a visualfunction testing device to be shown as a ninth embodiment.

FIG. 23 is a block diagram showing a configuration example of a visualfunction testing device to be shown as a tenth embodiment.

DESCRIPTION OF EMBODIMENTS

A description is made below of embodiments of the present disclosurewith reference to the drawings.

First Embodiment

A visual function testing device of a first embodiment of the presentdisclosure is a device that can implement a plurality of visual functiontests in a state where both eyes are opened, which is a state wherevisual performance is close to daily visual performance, and canevaluate the daily visual performance in many sides. This visualfunction testing device can perform the plurality of visual functiontests by itself. Such visual function tests are tests for functionswhich work for viewing, and are broadly classified into subjective testsand multisensitive tests. The subjective tests are tests such as visualacuity, visual field and binocular vision tests, which are frequentlyperformed in ophthalmic treatment. As opposed to this, the objectivetests are performed in such a case where a response of a patient cannotbe obtained or is unreliable since the patient is a baby or an infant.The visual acuity test includes a binocular visual acuity test and amonocular visual acuity test. The visual field test includes a binocularvisual field test and a monocular visual field test. Moreover, in thisvisual function testing device, a display that presents a visual targetimage has a dichoptic function. In such a way, the visual functiontesting device can switch and implement the monocular visual test andthe binocular visual test without using an occluder or the like. Notethat the visual target to be presented by the visual function testingdevice is an image or a video presented for the purpose of the visualfunction tests, and mentioned are a Landolt ring in the visual acuitytest, a radiant of the visual field test, and the like.

First, a description is made of a visual function testing device fortesting a binocular visual acuity and a binocular visual field as visualfunction test items by itself.

A description is made of a technical significance of this visualfunction testing device. In the conventional visual function tests,there have been testers dedicated for each of the visual function testitems. Accordingly, in the case of performing the plurality of visualfunction tests, such problems have occurred that a tester operator and apatient must move among the testers, the tester operator must learndifferent testing methods, and that test results cannot be integrated.Heretofore, there has been proposed a technology for realizing thevisual acuity test and the visual field test in such a manner that avisual target for the visual acuity test is presented on a liquidcrystal screen arranged on a center portion, and that a visual targetfor the visual field test is presented by a light source arranged on aperiphery thereof (Japanese Patent Laid-Open Publication No.2003-93344). However, this technology does not have a function to changea display size and display position of the visual target image inresponse to a viewpoint distance. Therefore, a viewpoint position isfixed, and the viewpoint position cannot be changed for each of thevisual function test items. In a general visual acuity test, a viewpointdistance between a visual acuity chart and an observer is defined to be5 meters (m).

Moreover, in the visual field test, a capability of presenting thevisual target within an approximate range where a viewing angle is 20degrees to 30 degrees is required in order to measure a central visualfield. The viewing angle is one in which a visible range is representedby an angle from an eye, and is a value that represents how wide a rangevisible from the front is.

That is to say, as shown in FIG. 1, when the visual acuity and fieldtests are implemented by the same device at a fixed viewpoint positionP, a presentation surface 2 a in which a viewing angle from a viewpointposition P apart therefrom by a distance A of 5 m is 20 degrees or morebecomes necessary. Then, a range of this presentation surface 2 abecomes a circle in which a diameter B is approximately 1.76 m. Whenthis circle in which the diameter B is approximately 1.76 m is presentedby a display (aspect ratio is 4:3), a screen size of 116 inches(4:3=breadth 2.358 m: height 1.769 m) or more is required. As describedabove, a configuration in which the viewpoint position P is fixed is notrealistic since a scale of a device configuration becomes large.

In this connection, upon receiving the viewpoint distance and visualangle of the observer, the present visual function testing device cancalculate a display size and display position of the visual targetimage, which correspond to the change of the viewpoint position P, andcan implement the binocular visual acuity test and the binocular visualfield test at an arbitrary viewpoint position P.

The visual function testing device as described above is configured, forexample, as shown in FIG. 2. The visual function testing device includesa control device 1 and a visual target image presentation unit 2 such asa liquid crystal display, which presents the visual target image.

The visual target image presentation unit 2 displays the visual targetimage. As shown in FIGS. 3( a) to 3(d), a shape of the presentationsurface of the visual target image presentation unit 2 may include aflat type as shown in FIG. 3( a), an arch type as shown in FIG. 3( b),and a dome type as shown in FIG. 3( c). Moreover, the shape concernedmay include a multi-surface type as shown in FIG. 3( d), in whichflat-type displays are combined with one another, or may be composed ofa head-mount type such as a head mount display. Note that themulti-surface type is composed of a polygon, and the number of surfacesis not limited to three.

Such a flat-type display has a feature that it is possible to present ahigh-resolution image. Such arch-type and dome-type displays caneffectively cover the visual field, and accordingly, have a feature thatit is possible to present a wide-visual-field image. Such amulti-surface type display has a feature that it is possible to presenta high-resolution and wide-visual-field image. Moreover, such ahead-mount type display has a feature that it is possible to present animage without being affected by external light. Note that, since thisvisual function testing device takes the viewpoint distance as an inputvalue, desirably, the head of the observer is fixed by mounting a chinrest and the like so that the viewpoint position (head position of theobserver) cannot fluctuate.

The control device 1 includes: a visual function test item selectionunit 11; a visual target image generation unit 12; a visual target imagerendering unit 13; a viewpoint distance input unit 14; and a visualangle input unit 15. These respective units are realized in such amanner that a CPU executes a program and the like, which are stored in aROM.

The visual function test item selection unit 11 selects the item of thevisual function test. As the visual function test item of FIG. 1, eitherof the binocular visual acuity and the binocular visual field isselected. The visual function test item selection unit 11 may include,for example, a keyboard and the like, which operate the control device1. In the visual function test item selection unit 11, an operation ofselecting any from the visual function test items displayed on thevisual target image presentation unit 2 is performed for the keyboard.In such a way, the visual function test item selection unit 11 suppliesinformation of the selected visual function test item to the visualtarget image generation unit 12.

The visual target image generation unit 12 generates a visual targetimage corresponding to the test item selected by the visual functiontest item selection unit 11. The visual target image generation unit 12outputs the visual target image, which is selected by the visualfunction test item selection unit 11 from among a plurality of prestoredvisual target images, to the visual target image rendering unit 13.Moreover, every time when the visual function test item is selected, thevisual target image generation unit 12 may newly generate the visualtarget image. Note that, in the case of using the Landolt ring or acomplicated pattern (animal picture, text or the like) as the visualtarget image, desirably, the Landolt ring or the complicated pattern isgenerated in advance. Furthermore, a simple pattern such as the radiantmay be generated in real time.

In the case where the visual acuity test is selected, the visual targetimage generation unit 12 generates a Landolt ring as shown in FIG. 4(a). The Landolt ring is a circle of which part is broken, and is astandard visual target for the visual acuity test. When a break with awidth of 1.5 mm in the Landolt ring with a diameter of 7.5 millimeters(mm) can be seen from a place apart therefrom by 5 m, visual acuity atthat time becomes 1.0. In the case where the visual field test isselected, the visual target image generation unit 12 generates a radiantas shown in FIG. 4( b). With regard to this visual target image, adisplay size C thereof is adjusted as will be described later.

The viewpoint distance input unit 14 inputs the distance between thevisual target image presentation unit 2 and the viewpoint of theobserver. The viewpoint distance input unit 14 may include, for example,the keyboard and the like, which operate the control device 1. In theviewpoint distance input unit 14, by visual recognition, input of theviewpoint distance between the viewpoint position of the observer andthe visual target image presentation unit 2 is performed for thekeyboard. In such a way, the viewpoint distance input unit 14 suppliesthe inputted viewpoint distance to the visual target image renderingunit 13.

The visual angle input unit 15 inputs the angle made by the visualtarget image and the viewpoint of the observer. That is to say, thevisual angle input unit 15 inputs such a visual angle which the observerrequires in order to see the visual target image. The visual angle inputunit 15 may include, for example, the keyboard and the like, whichoperate the control device 1. In the visual angle input unit 15, inputof the visual angle is performed for the keyboard. In such a way, thevisual angle input unit 15 supplies the inputted visual angle to thevisual target image rendering unit 13.

The visual target image rendering unit 13 renders the visual targetimage to be presented to the visual target image presentation unit 2. Atthis time, based on the viewpoint distance inputted by the viewpointdistance input unit 14 and on the visual angle inputted by the visualangle input unit 15, the visual target image rendering unit 13calculates the display size and display position of the visual targetimage, which correspond to the visual acuity or field test selected bythe visual function test item selection unit 11. Then, the visual targetimage rendering unit 13 renders the visual target image with thecalculated display size at the calculated display position. In such away, on the visual target image presentation unit 2, the visual targetimage with the display size corresponding to the inputted viewpointdistance and visual angle can be displayed at such a display position ofthe visual target image presentation unit 2 concerned, which correspondsto the inputted viewpoint distance and visual angle.

[Calculation Processing for Display Size]

Next, a description is made of processing for calculating the displaysize of the visual target image based on the viewpoint distance and thevisual angle.

As shown in FIG. 5, from the viewpoint distance A between the viewpointposition P of the observer and the presentation surface 2 a of thevisual target image presentation unit 2, and from trigonometricfunctions (Expression 1a, Expression 1b) of the visual angles θ in thelateral direction and the longitudinal direction, lateral andlongitudinal sizes B of the visual target image to be presented on thepresentation surface 2 a of the visual target image presentation unit 2are calculated. Expressions 1a and 1b are established as follows:

B _(W)=2×A×tan(θ_(W)/2)  (Expression 1a)

B _(H)=2×A×tan(θ_(H)/2)  (Expression 1b)

where B_(W) is a lateral size [mm], B_(H) is a longitudinal size [mm],θ_(W) is a lateral visual angle [degree], and θ_(H) is a longitudinalvisual angle [degree]. Note that, in FIG. 5, a screen of the visualtarget image presentation unit 2, which is other than the visual angle θof the observer, is shown as a non-presentation surface 2 b.

In the case where the visual target image is square, the display size Cjust needs to be decided by using a visual angle in at least onedirection between the longitudinal direction and the lateral directionin which visual angles are inputted by the visual angle input unit 15.However, in the case where the shape of the visual target image is ashape other than the square, it is necessary to input the visual anglesin both of the longitudinal direction and the lateral direction by thevisual angle input unit 15 in order to decide the display size C of thevisual target image concerned. Alternatively, the visual angle in one ofthe directions is inputted by the visual angle input unit 15, andfurther, the aspect ratio (4:3 and the like) is inputted by other means,whereby it is necessary to decide the display size C of the visualtarget image with the shape other than the square.

As shown in FIG. 4( c), in the case where the size of the visual targetimage to be generated by the visual target image generation unit 12 isdesignated as the lateral and longitudinal sizes C [mm], displaymagnifications D [%] of the visual target image to be presented on thepresentation surface 2 a of the visual target image presentation unit 2are calculated by Expression 2a and Expression 2b, which are describedbelow. In Expressions 2a and 2b, C_(W) is the size [pixel] in thelateral direction, C_(H) is the size [mm] in the longitudinal direction,D_(W) is such a lateral display magnification [%] of the visual targetimage, and D_(H) is such a longitudinal display magnification [%]thereof. The lateral size B_(W) and the longitudinal size B_(H) areobtained by Expression 1.

D _(W) =B _(W) /C _(W)  (Expression 2a)

D _(H) =B _(H) /C _(H)  (Expression 2b)

If this visual target image rendering unit 13 renders the visual targetimage by the display magnifications D, then the visual target imagerendering unit 13 can present the display size C, which corresponds tothe visual angle inputted by the visual angle input unit 15, on thevisual target image presentation unit 2. In such a way, even if aresolution of the visual target image presentation unit 2 is different,the visual function testing device can present the visual target imagewith the display size, which corresponds to the visual angle θ and theviewpoint distance, in conformity with the size of the pixels of thevisual target image presentation unit 2 concerned.

There is also a case where the size of the visual target image to begenerated by the visual target image generation unit 12 is designated bylateral and longitudinal resolutions E [longitudinal pixels×lateralpixels]. In this case, based on lateral and longitudinal screendimensions F [mm] of the visual target image presentation unit 2, and onlateral and longitudinal screen resolutions G of the visual target imagepresentation unit 2, lengths C of the visual target image are calculatedby Expressions 3a and 3b. In Expressions 3a and 3b, E_(W) is the lateralresolution of the visual target image, E_(H) is the longitudinalresolution thereof, F_(W) is the lateral screen dimension of the visualtarget image presentation unit 2, F_(H) is the longitudinal screendimension thereof, G_(W) is the lateral screen resolution of the visualtarget image presentation unit, and G_(H) is the longitudinal screenresolution thereof.

C _(W) =E _(W) ×F _(W) /G _(W)  (Expression 3a)

C _(H) =E _(H) ×F _(H) /G _(H)  (Expression 3b)

The visual target image rendering unit 13 substitutes the display sizes,which are calculated by Expressions 3a and 3b, into Expressions 2a and2b. In such a way, the visual target image rendering unit 13 cancalculate the display magnifications D of the visual target image to bepresented on the screen of the visual target image presentation unit 2.If the visual target image rendering unit 13 renders the visual targetimage by the magnifications thus calculated, then the visual targetimage rendering unit 13 concerned can present the visual target image atthe display sizes C corresponding to the visual angle.

[Calculation Processing for Display Position]

Next, a description is made of processing for calculating the displayposition of the visual target image based on the viewpoint distance andthe visual angle.

As shown in FIG. 6, the display position of the visual target image isdesignated by an XY coordinate system that takes, as an origin, a screencenter of the visual target image presentation unit 2. FIG. 6 shows astate where the viewpoint position P of the observer is directlyconfronted to the screen center C (X₀, Y₀) of the presentation screen 2a of the visual target image presentation unit 2. The viewpoint distancebetween the viewpoint position P and the screen center C becomes A.Coordinate values (X, Y) of intersection points 2 a-1 to 2 a-4 between arange 2 a′, which is represented by the visual angles θ_(W) (lateraldirection) and θ_(H) (longitudinal direction) of the observer, and anX-axis and a Y-axis on the presentation surface 2 a of the visual targetimage presentation unit 2 are calculated by Expressions 4a and 4b, whichare described below.

X=±A×tan(θ_(W)/2)−X ₀  (Expression 4a)

Y=±A×tan(θ_(H)/2)−Y ₀  (Expression 4b)

By Expressions 4a and 4b, a coordinate value X₁ of the intersectionpoint 2 a-3, a coordinate value X₂ of the intersection point 2 a-4, acoordinate value Y₁ of the intersection point 2 a-1 and a coordinatevalue Y₂ of the intersection point 2 a-2 can be calculated while taking,as a center, the screen center C (origin) on the presentation surface 2a of the visual target image presentation unit 2. The intersectionpoints are four in total, in which two are located on positive andnegative sides on the X-axis, respectively, and other two are located onpositive and negative sides on the Y-axis, respectively.

As shown in FIG. 7, cross-ruled grid lines 2 c are set, which take, asreferences, squares formed of the origin as the screen center C on thepresentation surface 2 a of the visual target image presentation unit 2,and of the four coordinate values [(X₁, 0), (X₂, 0), (0, Y₁), (0, Y₂)].Coordinates on the X-axis and the Y-axis, which are apart from theorigin by one square, become boundaries of a viewing angle of the visualangle θ in which the origin is taken as a fixation point. Coordinates onthe X-axis and the Y-axis, which are apart from the origin by twosquares, become boundaries of a viewing angle 2θ in which the origin istaken as the fixation point. That is to say, the respective latticepoints on the grid lines 2 c are set on a display position of the visualtarget image, whereby, based on the viewpoint distance and the visualangle, which are inputted by the viewpoint distance input unit 14 andthe visual angle input unit 15, unit grid widths with respect to theX-axis and the Y-axis can be calculated, and such a cross-ruledcoordinate system can be formed. Thereafter, the visual target imagerendering unit 13 just needs to designate on which lattice point thevisual target image is to be displayed.

In this visual function testing device, input values of the visualangles in the lateral direction (X-axis direction) and the longitudinaldirection (Y-axis direction) to the visual angle input unit 15 may beindividually set. In the case where both of the visual angles in thelateral direction (X-axis direction) and the longitudinal direction(Y-axis direction), which are inputted by the visual angle input unit15, are the same, a shape of the lattices to be formed of the grid lines2 c becomes square. In the case where the visual angles in the lateraldirection (X-axis direction) and the longitudinal direction (Y-axisdirection), which are inputted by the visual angle input unit 15, aredifferent from each other, the shape of the lattices to be formed of thegrid lines 2 c becomes rectangular.

The origin of the presentation surface 2 a is not limited to the screencenter C on the presentation surface 2 a of the visual target imagepresentation unit 2. For example, as shown in FIG. 8( a), a position Con the presentation surface 2 a, which is directly confronted to acenter position E_(C) between a position E_(L) of a left eye betweenboth eyes and a position E_(R) of a right eye between both of them maybe set as the origin. Moreover, as shown in FIG. 8( b), the origin maybe set on a position C on the presentation surface 2 a, which isdirectly confronted to such a left eye position E_(L) or such a righteye position E_(R). Furthermore, the origin may be set on an arbitraryposition on the presentation surface 2 a. As a calculation method of theunit grid widths when the origin is set as described above, distancedifferences between the newly set origin and the screen center C on thepresentation surface 2 a of the visual target image presentation unit 2are adapted to the four coordinate values (X₁, X₂, Y₁, Y₂) calculated byExpressions 4a and 4b. That is to say, such a distance difference in theX-axis direction is added to Expression 4a, and such a distancedifference in the Y-axis direction is added to Expression 4b.

[Visual Acuity Test]

Next, a description is made of the visual acuity test by theabove-mentioned visual function testing device.

The visual acuity test is a test method of evaluating a capability(minimum resolvable threshold) of resolving and recognizing two pointsor two lines. An angle made by two points or two lines, which are barelydeterminable by an eye, with respect to the eye is represented by a“minute (= 1/60 degrees)”, and an inverse number thereof is evaluated asvisual acuity. As the existing test method, when a break with a width of1.5 mm in the Landolt ring with a diameter of 7.5 millimeters (mm) and athickness of 1.5 mm can be seen from a place apart therefrom by 5 m,visual acuity at that time becomes 1.0. In this case, as shown in FIG.9, the break with a width of 1.5 mm is equivalent to one minute of thevisual angle.

In the visual acuity test, based on the viewpoint distance inputted bythe viewpoint distance input unit 14 and on the visual angle inputted bythe visual angle input unit 15, the control device 1 sets the displaysize and display position of the visual target image (for example, theLandolt ring). With regard to the display size, a size corresponding tothe visual acuity is set. With regard to the display position, anarbitrary position may be set; however, a center position of the visualtarget image presentation unit 2 is desirable. Note that, with regard tothe above-mentioned visual function test, the binocular visual acuitytest is implemented as the visual acuity test since such a blockingfunction to present the visual target image for each eye is notprovided. The monocular visual acuity test is realizable by a visualfunction testing device to be described later.

In the visual acuity test of the visual function testing device of thisembodiment, a resolution width between two points or two lines is set bythe visual angle θ corresponding to the visual acuity J as shown inExpression 5 to be described below. The visual angle θ is inputted bythe visual angle input unit 15. Then, the visual function testing devicepresents the visual target image with the display size C fitted to thevisual angle θ concerned on the visual target image presentation unit 2.

J=1/θ  (Expression 5)

Moreover, the visual function testing device adds a function tocalculate the visual angle θ from the visual acuity J by backcalculation of Expression 5. In such a way, the display size C can becalculated from the visual acuity J.

Shown below is a method for displaying the Landolt ring with a diameterof 7.5 mm, a thickness of 1.5 mm and a break of 1.5 mm so that the breakof 1.5 mm can be visually recognized as a visual angle of 1 minute fromthe viewpoint distance of A m (so as to establish a display size thatenables the visual acuity of 1.0 to be tested). Here, the visual targetimage generation unit 12 generates the Landolt ring in response to thatthe visual function test item selection unit 11 selects the visualacuity test.

(1) In the event of generating the visual target image by the visualtarget image creation unit 12, the size of the visual target image(Landolt ring) is designated by the length C. At this time, acalculation method of the display magnifications D for measuring desiredvisual acuity by seeing the visual target image presentation unit 2 fromthe viewpoint distance inputted by the viewpoint distance input unit 14is as follows.

In a general visual acuity test, while the width (resolution width) ofthe break of the Landolt ring is 1.5 mm, the diameter of the Landoltring is defined as 7.5 mm (5 times). Therefore, in order to display thebreak of the Landolt at the visual angle of 1 minute ( 1/60 degrees) onthe visual target image presentation unit 2, the visual target image ofthe Landolt ring just needs to be displayed at a visual angle of 5minutes (5 times). The size B of the visual target image to be visuallyrecognized at the visual angle of 5 minutes from the viewpoint distanceof A m is calculated from Expression 1 by using the visual angle θ=5minutes. Note that, in the case where the visual target image is theLandolt ring, the lateral and longitudinal length B of the Landolt ringare equal to each other, and accordingly, only either one of the lateraland longitudinal lengths B just needs to be obtained. Then, such adisplay magnification D of the Landolt ring on the visual target imagepresentation unit 2 is calculated from either one of Expressions 2a and2b by using this length B of the visual target image and the designatedsize C of the visual target image.

(2) In the event of generating the visual target image by the visualtarget image generation unit 12, the size of the visual target image(Landolt ring) is designated by an image resolution E. At this time, thecalculation method of the display magnifications D for measuring desiredvisual acuity by seeing the visual target image presentation unit 2 fromthe viewpoint distance inputted by the viewpoint distance input unit 14is as follows.

In a similar way to (1), the size B of the visual target image to bevisually recognized with a size of the visual angle θ of 5 minutes fromthe viewpoint distance of A m is calculated by Expression 1. Note that,in the case where the visual target image is the Landolt ring, thelateral and longitudinal length B of the Landolt ring are equal to eachother, and accordingly, only either one of the lateral and longitudinallengths B just needs to be obtained. From either one of Expressions 3aand 3b, the size B of the visual target image, which is designated bythe image resolution E, is converted into the display size C from such ascreen dimension F and screen resolution G of the visual target imagepresentation unit 2, and further, from either one of Expressions 2a and2b, the display magnification D is calculated from the size B of thevisual target image and the display size C.

If the resolution width (break) of the visual target (Landolt ring)displayed on the visual target image presentation unit 2 can beperceived under the display magnification D calculated by (1) or (2),then the visual acuity is 1.0. In order to establish a test conditionsimilar to that of the current visual acuity test, the viewpointdistance A between the visual target image presentation unit 2 and theobserver just needs to be set at 5 m.

[Visual Field Test]

The visual field test is a test for measuring a sensitivity distributionmap of the vision by a response of a subject to the presentation of thevisual target. In this visual field test, the visual function testingdevice measures a perceivable range without moving the eye. A visualfield measurement method includes dynamic visual field measurement andstatic visual field measurement. In the dynamic visual fieldmeasurement, the visual target is moved, and a region where certainsensitivity is exhibited is measured. In the static visual fieldmeasurement, the sensitivity is measured at fixed points without movingthe visual target.

In the visual field test, based on the viewpoint distance inputted bythe viewpoint distance input unit 14 and on the visual angle valueinputted by the visual angle input unit 15, the control device 1 setsthe display size and display position of the visual target image (forexample, the radiant). The display size just needs to be set at anarbitrary visual angle. The display position is set on a lattice inwhich a fixation point is taken as an origin, and a grid width is set bythe viewpoint distance and the visual angle. Note that, with regard tothe above-mentioned visual function test, the binocular visual fieldtest is implemented as the visual field test since such a blockingfunction to present the visual target image for each eye is notprovided. The monocular visual field test is realizable by a visualfunction testing device to be described later.

In the visual field test of the visual function testing device of thisembodiment, as shown in FIG. 10, the observer allows a fixation point Das the origin to be displayed on the visual target image presentationunit 2. The observer gazes this fixation point D. In a state where theviewpoint of the observer is fixed as described above, the visual targetE (radiant) is displayed on a position on the lattice in which thefixation point D is taken as the origin. In such a way, the visualfunction testing device tests whether or not the observer can perceivethe visual target E.

The fixation point D as the origin and the visual target E are displayedon intersection points on grid lines 2 c with a grid width K, which areformed on the visual target image presentation unit 2. The grid lines 2c are similar to those shown in FIG. 7 mentioned above. This grid widthK is calculated based on the visual distance A and the visual angle θ inaccordance with the above-described Expression 4 (X=±A×tan (θ/2)−X₀,Y=±A×tan(θ/2)−Y₀).

Moreover, with regard to a visual target position to be set on theintersection point of the grid lines 2 c, the visual function testingdevice can arbitrarily set a display order of the visual target. That isto say, the visual function testing device can display the visual targetimage in a random display order within a range of a visual field desiredto be measured. Moreover, the visual function testing device may limitthe display position of each visual target image to an arbitrary range.

Furthermore, in a similar way to a quantitative dynamic visual fieldtest, this visual function testing device may create a plurality ofvisual targets (radiants) with arbitrary display size and brightnessvalue in advance, and may implement the visual field test by changingthe size and brightness of the visual targets. In such a way, the visualfunction testing device can test perception sensitivity in the visualfield test.

Note that, in a similar way to the visual field test, designation of thedisplay position of the visual target image in the visual acuity test isperformed by designating the lattice point on which the visual targetimage is to be displayed. In the usual visual acuity test, the visualacuity target (Landolt ring) is displayed on the screen center C of thevisual target image presentation unit 2; however, in the course of thevisual acuity test, the visual acuity target is sometimes displayed on aposition apart from the screen center C. For example, in such a case oftesting visual acuity when the observer faces upward, the Landolt ringis displayed on a lattice point shifted upward from the screen center C.

As described above, in accordance with the visual function testingdevice shown as the first embodiment, based on the viewpoint distanceand the visual angle, the display size and display position of thevisual target image are calculated, and the visual target image isrendered. Accordingly, the plurality of visual function tests can beperformed by the same device in a state where both eyes are opened and astate where the visual performance is close to the daily one withoutblocking the visual field or restricting the viewing field.

Second Embodiment

Next, a description is made of a visual function testing deviceaccording to a second embodiment. Note that the same reference numeralsare assigned to similar portions to those of the above-mentioned firstembodiment, whereby a detailed description thereof is omitted.

The visual function testing device to be shown as the second embodimentis a device that can perform visual function tests of monocular visualacuity, monocular visual field and stereopsis in addition to thoseperformed by the visual function testing device shown as theabove-mentioned first embodiment.

As shown in FIG. 11, this visual function testing device is differentfrom the above-mentioned visual function testing device in that a visualtarget image selection presentation unit 20 is provided in the controldevice 1. Moreover, in this visual function testing device, the visualtarget image generation unit 12 has a binocular visual target imagegeneration function to generate visual target images for each of theright eye and left eye of the subject. Furthermore, the visual targetimage presentation unit 2 has a dichoptic visual target imagepresentation function to perform dichoptic viewing for the binocularvisual target images for the right eye and the left eye, which aregenerated by the binocular visual target image generation function ofthe visual target image generation unit 12, and to present the binoculartarget images, which are subjected to the dichoptic viewing, for each ofthe eyes corresponding thereto.

This visual target image presentation unit 2 can allow the right eye andleft eye of the observer to separate and visually recognize a righteye-use visual target image and a left eye-use visual target image,respectively. The visual target image presentation unit 2 may include,for example, a display and a projection system, which use the currentdichoptic method such as a polarization method, a spectrum method, and atime division method, and may be composed of a head-mount type such as ahead mount display. The observer is allowed to put on glassescorresponding to the method to be adopted by the visual target imagepresentation unit 2. In such a way, the visual function testing deviceincludes a dichoptic function to present visual target images, which aredifferent from each other, individually to the right eye and left eye ofthe observer.

The visual target image selection presentation unit 20 selects displayor non-display of the right-eye or left-eye visual target image, whichis to be presented by the dichoptic visual target image presentationfunction of the visual target image presentation unit 2, independentlyof each other. The visual target image selection presentation unit 20may include, for example, a keyboard and the like. In the visual targetimage selection presentation unit 20, an operation of selecting eitherof the display and non-display of the right-eye or left-eye visualtarget image displayed on the visual target image presentation unit 2 isperformed for the keyboard. In such a way, the visual target imageselection presentation unit 20 supplies information on the selecteddisplay or non-display to the visual target image generation unit 12.

In the visual function testing device as described above, the visualtarget image selection presentation unit 20 displays a visual targetimage corresponding to the monocular visual acuity test, the monocularvisual field test or the stereopsis test, which is selected by thevisual function test item selection unit 11.

Specifically, in the visual function testing device, the monocularvisual acuity test, the monocular visual field test or the stereopsistest is selected by the visual function test item selection unit 11.Then, the visual target image generation unit 12 generates the righteye-use visual target image and the left eye-use visual target image,which correspond to the test thus selected (binocular visual targetimage generation function).

In the case where the visual function test only for one eye is selectedby the visual target image section presentation unit 20, the visualtarget image generation unit 12 generates the selected right eye-usevisual target image or left eye-use visual target image, and suppliesthe generated right eye- or left eye-use visual target image to thevisual target image rendering unit 13. In the case where the stereopsistest is selected, the visual target image generation unit 12 generatesboth of the right eye-use visual target image and the left eye-usevisual target image, and supplies the generated right eye- and lefteye-use visual target images to the visual target image rendering unit13.

The visual target image generation unit 12 generates both of the righteye-use visual target image and the left eye-use visual target image,and converts one of the visual target images, which is selected as thenon-display by the visual target image selection presentation unit 20,into a blank image with the same color as a background color.

Note that the visual target image selection presentation unit 20 may beconnected to the visual target image rendering unit 13, and may allowthe visual target image rendering unit 13 to render only the righteye-use visual target image or the left eye-use visual target image.Moreover, the visual target image selection presentation unit 20 may beconnected to the visual target image presentation unit 2, and may allowthe visual target image presentation unit 2 to display only the righteye-use visual target image or the left eye-use visual target image.

The visual target image rendering unit 13 individually renders the righteye-use visual target image and the left eye-use visual target image,which are supplied from the visual target image generation unit 12(dichoptic image rendering function). Rendering data corresponding tothe right eye-use visual target image and rendering data correspondingto the left eye-use visual target image are supplied to the visualtarget image presentation unit 2.

By using the rendering data individually corresponding to the righteye-use visual target image and the left eye-use visual target image,the visual target image presentation unit 2 displays the right eye-usevisual target image and the left eye-use visual target image (dichopticimage presentation function). In such a way, the right eye-use visualtarget image is visually recognized only by the right eye of theobserver, and the left eye-use visual target image is visuallyrecognized by the left eye of the observer.

In the visual function testing device as described above, in themonocular visual acuity test and the monocular visual field test,generation of the visual target image and setting of the display sizeand the display position are performed in a similar way to theabove-mentioned visual function testing device. Then, the right eye-usevisual target image or the left eye-use visual target image is madevisually recognizable in accordance with the selection of the visualtarget image selection presentation unit 20, whereby the monocularvisual acuity test and the monocular visual field test are realized.

Next, a description is made of the stereopsis test by the visualfunction testing device shown in FIG. 11. In the stereopsis test, arelative depth perception to be caused by fusing images with a binocularparallax, which are individually presented to the left and right eyes,is tested. This parallax is a positional change of image formation on aretina owing to a movement of a relative position between the eye and anobject or to a difference therebetween. With regard to this parallax,whether the object is near or far can be perceived by the binocularparallax represented by an angle made by lines of sight of both eyeswith respect to the object.

In the stereopsis test, with regard to the display size C of the visualtarget image, the arbitrary size B just needs to be set based on thevisual angle inputted by the visual angle input unit 15. Moreover, inthe stereopsis test, with regard to the display position, acenter-to-center distance (parallax) between the visual target images ofthe left and the right eye is set based on the visual angle inputted bythe visual angle input unit 15.

In this stereopsis test of the visual function testing device, as shownin FIG. 12, among a plurality of dichoptic visual target images 100 a to100 d presented on the visual target image presentation unit 2, anarbitrary parallax amount is imparted to one visual target image denotedby reference numerals 100 d and 100 d′.

The display size C of such a visual target image 100 is calculated byExpression 2 or Expression 3, which is described above, in such a mannerthat an arbitrary size is set by the visual angle θ inputted by thevisual angle input unit 15. Moreover, with regard to the parallax amountthat allows the recognition of the stereopsis, as shown in FIG. 13, thevisual angle θ inputted by the visual angle input unit 15 is set, andthe display position is calculated by the viewpoint distance A inputtedby the viewpoint distance input unit 14. As described above, the visualfunction testing device inputs the visual angle θ and the viewpointdistance A, and can thereby adjust such a distance between the visualtarget images 100 d and 100 d′ for testing the stereopsis. In such away, such a stereoscopic function can be tested based on whether or notthere is a relative depth perception with respect to a micro parallaxamount.

In accordance with this visual function testing device, by the dichopticimage presentation function of the visual target image presentation unit2, the functions of the monocular visual acuity and the monocular visualfield can be tested in a state where both eyes are opened withoutrestricting the visual field, and in addition, the stereopsis test canbe implemented by the same device.

Third Embodiment

Next, a description is made of a visual function testing deviceaccording to a third embodiment. Note that the same reference numeralsare assigned to similar portions to those of the above-mentionedembodiments, whereby a detailed description thereof is omitted.

This visual function testing device is a device that can perform visualfunction tests of a binocular vision and an eye position in addition tothose performed by the visual function testing device shown as theabove-mentioned second embodiment.

Such a binocular vision test is a test that evaluates whether or notimages given to the retinas of the respective left and right eyes can beseen as a single image in a central nervous system of vision (brain),and the test is performed for each of items such as simultaneous vision,(sensory, motor) fusions, stereopsis, and retinal correspondence.

The simultaneous vision refers to a capability of recognizing two typesof images A and B as one image at the time of seeing the image A by theright eye and seeing the image B by the left eye. Moreover, thestereopsis is a capability of stereoscopically seeing an object byrecognizing the parallax to be caused by that positions of the left andright eyes are different from each other. The fusion is furtherclassified into the motor fusion and the sensory fusion. The motorfusion is a capability of recognizing a left eye-use image and a righteye-use image, which are presented at positions apart from each other,as one image by eye movements as congestion (cross eye) and divergence(separate eye). The sensory fusion is a capability of recognizing thesame image, which is changed in appearance such as a size and a blurdifference and is presented to the left and right eyes, as one image bya function of the brain.

For example, in the sensory fusion test, with regard to a test(aniseikonia test) of a size difference between visual target sizesshown in FIG. 14, to a test of the blur difference between visualtargets shown in FIG. 15, and to a test for a positional shift, a righteye-use visual target image and a left eye-use visual target image,between which the blur difference is inherent, are generated in advance.Then, in a similar way to the visual function testing device shown asthe above-mentioned second embodiment, the right eye-use visual targetimage and the left eye-use visual target image, which are generated bythe visual function test item selection unit 11, are rendered by thevisual target image rendering unit 13, and by the visual target imagepresentation unit 2, the right eye-use visual target image and the lefteye-use visual target image are displayed in accordance with apredetermined dichoptic method. In such a way, the visual functiontesting device allows only the right eye of the observer to visuallyrecognize the right eye-use visual target image, and allows only theleft eye of the observer to visually recognize the left eye-use visualtarget image.

As shown in FIG. 16, this visual function testing device includes avisual target image operation unit 21. This visual target imageoperation unit 21 changes at least either of the display size anddisplay position of the visual target image by an operation of a user.The visual target image operation unit 21 is composed of an operationdevice such as a mouse and a button, which is operated by the user, andoutputs a signal of allowing the user to move the visual target image,which is presented by the visual target image presentation unit 2, inresponse to visual performance of the visual target image concerned.Then, the visual target image rendering unit 13 updates the position ofthe visual target image, which is to be presented on the visual targetimage presentation unit 2, based on the signal supplied from the visualtarget image operation unit 21.

In the visual function testing device as described above, the binocularvision test or the eye position test is selected by the visual functiontest item selection unit 11. In this case, in accordance with thedisplay size or display position of the visual target image, which ischanged by the visual target image operation unit 21, the visual targetimage rendering unit 13 changes the visual target image to the displaysize and the display position, which is calculated by the visual targetimage rendering unit 13, and then renders the visual target imageconcerned.

As described above, in accordance with the visual function testingdevice shown as the third embodiment, the display size and displayposition of the visual target image can be changed by the operation ofthe user. In such a way, the visual function testing device becomescapable of performing the binocular vision tests (simultaneous visiontest, motor fusion test, sensory fusion test) and the eye position testby itself. Note that, with regard to grid lines to be displayed at theeye position test, the grid lines 2 c are displayed on the presentationsurface 2 a in a similar way to the visual function testing device shownas the first embodiment.

Next, a description is made of a visual function testing deviceaccording to a fourth embodiment. Note that the same reference numeralsare assigned to similar portions to those of the above-mentionedembodiments, whereby a detailed description thereof is omitted.

As shown in FIG. 17, this visual function testing device includes avisual target image adjustment unit 22 that adjusts the visualperformance of the visual target image, which is to be presented on thevisual target image presentation unit 2, in addition to those performedby the visual function testing devices shown as the above-mentionedembodiments.

The visual target image adjustment unit 22 is a unit for adjustingbrightness, contrast, color or transparency of the visual target image.The visual target image adjustment unit 22 supplies a control signal ofadjusting the brightness, contrast, color or transparency of the visualtarget image to the visual target image generation unit 12. For example,the visual target image adjustment unit 22 is composed of an operationdevice such as a keyboard and a mouse. The visual target imageadjustment unit 22 is operated by the user while the user is seeing thevisual target image displayed on the visual target image presentationunit 2, and thereby adjusts the visual target image.

Based on the control signal supplied from the visual target imageadjustment unit 22, the visual target image generation unit 12 adjuststhe brightness, contrast, color or transparency of the visual targetimage generated in response to the selection of the visual function testitem selection unit 11. The adjusted visual target image is supplied tothe visual target image rendering unit 13, is then rendered, and ispresented to the visual target image presentation unit 2.

In accordance with the visual function testing device as describedabove, the brightness, contrast, color and transparency of the visualtarget image are adjusted by the operation of the user, whereby thesensitivity of the visual function can be tested by the change of thevisual target image.

Fifth Embodiment

Next, a description is made of a visual function testing deviceaccording to a fifth embodiment. Note that the same reference numeralsare assigned to similar portions to those of the above-mentionedembodiments, whereby a detailed description thereof is omitted.

As shown in FIG. 18, this visual function testing device includes aviewpoint distance calculation unit 23 in place of the viewpointdistance input unit 14, and further, includes a viewing angle input unit24.

In this visual function testing device, in the case where the visualfield test is selected by the visual function test item selection unit11, the viewing angle input unit 24 inputs a viewing angle desired to betested in the visual field test concerned. This viewing angle input unit24 may include, for example, a keyboard, a mouse, a remote controllerand the like, which are to be operated by the user, and inputs viewingangle desired to be tested by the user.

The viewpoint distance calculation unit 23 calculates a viewpointdistance necessary to implement the visual field test at the viewingangle, which is inputted by the viewing angle input unit 24, in thescreen dimensions of the visual target image presentation unit 2. Atthis time, as shown in Expression 1 (B=2×A×tan(θ/2)), the viewpointdistance calculation unit 23 receives 0 as the viewing angle inputted bythe viewing angle input unit 24. In response to this, the viewpointdistance calculation unit 23 calculates Expression 1 by using 0 as theviewing angle concerned, and calculates the viewpoint distance A.

As described above, in response to that the visual field test isselected, and that the viewing angle desired to be tested is inputted,the visual function testing device can present the viewpoint distance,at which the viewing angle concerned can be tested, to the user. In sucha way, in the case where a wide viewing angle is desired to be tested,the visual function testing device can prompt the user to bring theviewpoint position P close to the visual target image presentation unit2. Hence, in accordance with this visual function testing device, thevisual field test can be performed by simple operations without settingcomplicated conditions.

Sixth Embodiment

Next, a description is made of a visual function testing deviceaccording to a sixth embodiment. Note that the same reference numeralsare assigned to similar portions to those of the above-mentionedembodiments, whereby a detailed description thereof is omitted.

As shown in FIG. 19, this visual function testing device includes aviewpoint distance calculation unit 23 in place of the viewpointdistance input unit 14, and further, includes a visual acuity input unit25.

In the case where the visual acuity test is selected by the visualfunction test item selection unit 11, the visual acuity input unit 25inputs visual acuity for use in the visual acuity test concerned. Thisvisual acuity input unit 25 may include, for example, a keyboard, amouse, a remote controller and the like, which are to be operated by theuser, and inputs visual acuity desired to be tested by the user.

The viewpoint distance calculation unit 23 calculates the viewpointdistance A required to implement the visual acuity test at the visualacuity, which is inputted by the visual acuity input unit 25, in theresolution of the visual target image presentation unit 2. It isnecessary for the viewpoint distance calculation unit 23 to set ashorter viewpoint distance A as the visual acuity desired to be testedis lower, and to calculate a longer viewpoint distance A as the visualacuity desired to be tested is higher.

It is necessary for such an image presentation resolution of the image,which is to be presented by this visual function testing device, tosatisfy a predetermined visual acuity conversion value H. This visualacuity conversion value H is a value that indicates to which extent ofvisual acuity one pixel of the visual target image presentation unit 2corresponds. This visual acuity conversion value H becomes higher as theimage presentation resolution of the visual target image presentationunit 2 is higher since a finer visual target mage can be presented.

In order that the observer can measure the desired visual acuity, aresolution of the visual target image presentation unit 2, which is forallowing distinguishment thereof by the visual acuity concerned, becomesnecessary. Hence, in the case where higher visual acuity is desired tobe measured for the observer, a higher resolution of the visual targetimage presentation unit 2 becomes necessary. A description is made belowof a calculation method of this visual acuity conversion value H.

The visual acuity is spatial resolving power of the viewing angle. Here,as shown in FIG. 5, an angle (hereinafter, a visual angle) made withrespect to the viewpoint position P is defined as θ. As units of thisvisual angle, a “minute” and a “second” obtained by dividing this“minute” into equal 60 parts are used. A value of this “minute” becomes“60 minutes” in the case where the visual angle θ is 1 degree.

In usual, a minimum value (minimum resolvable threshold) of a distancebetween two identifiable objects is represented by the visual angle, andan inverse number thereof becomes a visual acuity value. That is to say,visual acuity at which an interval of 1 minute as the visual angle canbe identified is defined as 1.0, if an interval of a 0.5 minute can beidentified, then the visual acuity value is 2.0, and if only an intervalof 2 minutes can be identified, then the visual acuity value is 0.5.

When such a relationship between the visual acuity and the visual angleis applied to presentation resolving power of the image to be displayedby the visual function testing device, then, the minimum resolvablethreshold is represented by the size of one pixel. Then, an inversenumber of the visual angle (unit: minute) with respect to the size ofone pixel becomes the visual acuity.

Hence, a visual acuity conversion value H obtained by converting suchimage display resolving power into the visual acuity is defined by animage presentation visual angle θ[degree] and an image presentationresolution X [pixel] as shown in Expression 6 to be described below.

H=1/((θ×60)/X)=X/(θ×60)  (Expression 6)

The image presentation visual angle θ in Expression 6 that representsthis visual acuity conversion value H is defined as in Expression 7 andExpression 8 by the distance A [mm] between the observer and thepresentation surface 2 a.

tan(θ/2)=(B/2)/A=B/2A  (Expression 7)

θ=2×tan⁻¹(B/2A)  (Expression 8)

Then, when the visual angle θ of Expression 8 is substituted toExpression 6, then the visual acuity conversion value H is representedas in Expression 9 to be described below.

H=X/(2×tan⁻¹(B/2A)×60)=X/(120×tan⁻¹(B/2A))  (Expression 9)

That is to say, as shown in Expression 10 to be described below,

X=120×H×tan⁻¹(B/2H)  (Expression 10)

As described above, if the visual acuity conversion value H desired tobe displayed, the width B of the presentation surface 2 a, and thedistance A between the observer and the presentation surface 2 a arespecified, then the image presentation resolution X is uniquelydetermined.

In accordance with this visual function testing device, if the observerinputs the visual acuity (visual acuity conversion value) desired to betested by the visual acuity test, then the viewpoint distance A forensuring the distance that enables the visual acuity test concerned canbe presented. Hence, in accordance with this visual function testingdevice, the visual acuity test can be performed by simple operationswithout setting complicated conditions.

Seventh Embodiment

Next, a description is made of a visual function testing deviceaccording to a seventh embodiment. Note that the same reference numeralsare assigned to similar portions to those of the above-mentionedembodiments, whereby a detailed description thereof is omitted.

As shown in FIG. 20, this visual function testing device includes aviewpoint distance calculation unit 23 in place of the viewpointdistance input unit 14, and further, includes a parallax input unit 26.

In the case where the stereopsis test is selected by the visual functiontest item selection unit 11, the parallax input unit 26 inputs aparallax for use in the stereopsis test concerned. This parallax inputunit 26 may include, for example, a keyboard, a mouse, a remotecontroller and the like, which are to be operated by the user, andinputs a parallax desired to be tested by the user.

The viewpoint distance calculation unit 23 calculates the viewpointdistance A required to implement the stereopsis test at the parallax,which is inputted by the parallax input unit 265, in the resolution ofthe visual target image presentation unit 2. At this time, the visualfunction testing device can calculate a minimum presentation visualangle with respect to the viewpoint distance A between the viewpointposition P and the presentation surface 2 a by the inverse number of thevisual acuity conversion value H in the above-mentioned embodiment. Itis necessary for the viewpoint distance calculation unit 23 to set alonger viewpoint distance A as the parallax desired to be tested issmaller, and to calculate a shorter viewpoint distance A as the parallaxdesired to be tested is larger.

When the parallax desired to be measured by the user is inputted by theparallax input unit 26, the visual function testing device as describedabove can obtain the viewpoint distance A, which enables the parallaxconcerned to be measured, by the viewpoint distance calculation unit 23,and can present the viewpoint distance A for ensuring the parallaxdesired to be tested. Hence, in accordance with this visual functiontesting device, the stereopsis test can be performed by simpleoperations without setting complicated conditions.

Eighth Embodiment

Next, a description is made a visual function testing device accordingto an eighth embodiment. Note that the same reference numerals areassigned to similar portions to those of the above-mentionedembodiments, whereby a detailed description thereof is omitted.

As shown in FIG. 21, this visual function testing device is a devicethat further includes a viewpoint distance measurement unit 27 incomparison with the visual function testing device shown as theabove-mentioned first embodiment. This viewpoint distance measurementunit 27 measures a distance between the visual target image presentationunit 2 and the viewpoint position P of the observer. The viewpointdistance measurement unit 27 inputs the current viewpoint position Pthus measured to the viewpoint distance input unit 14. For example, theviewpoint distance measurement unit 27 measures a head position of theobserver, and calculates the viewpoint distance from the head positionconcerned. Alternatively, the viewpoint distance measurement unit 27 maybe a distance sensor provided on dichoptic glasses put on by theobserver. In such a way, the viewpoint distance input unit 14 canautomatically input the viewpoint distance.

As described above, in accordance with the visual function testingdevice, it is not necessary to designate the viewpoint position P inadvance, and the visual function test corresponding to the head positionof the observer or the actual viewpoint position P can be implemented.Moreover, in the above-described embodiments shown in FIG. 18 to FIG.20, the necessary viewpoint distances A are calculated in response tothe viewing angle, the visual acuity and the parallax, which require tobe tested, and meanwhile, in accordance with this visual functiontesting device, a viewing angle, visual acuity and a parallax, for whichtesting is possible with respect to the current viewing distance A, canbe presented on the contrary.

Ninth Embodiment

Next, a description is made of a visual function testing deviceaccording to a ninth embodiment. Note that the same reference numeralsare assigned to similar portions to those of the above-mentionedembodiments, whereby a detailed description thereof is omitted.

As shown in FIG. 22, this visual function testing device includes avisual target image selection storage unit 28, a visual target imagestorage unit 29, a display setting storage unit 30, and a display ordersetting unit 31 in addition to the constituents of the visual functiontesting device of the above-mentioned second embodiment.

The visual target image storage unit 29 stores the visual target imagegenerated by the visual target image generation unit 12.

The display setting storage unit 30 stores the display size and displayposition of the visual target image, which are calculated by using theviewpoint position P inputted by the viewpoint distance input unit 14,and the visual angle inputted by the visual angle input unit 15.

The visual target image selection storage unit 28 stores the display ornon-display of the visual target image for each of the right eye and theleft eye, which is set by the visual target image selection presentationunit 20.

The display order setting unit 31 receives the information of thedisplay or non-display of the visual target image for each of the righteye and the left eye, which is stored in the visual target imageselection storage unit 28, the visual target image stored in the visualtarget image storage unit 29, and the display size and display positionof the visual target image, which is stored in the display settingstorage unit 30. Then, by using these data, the display order settingunit 31 sets a display order of the visual target image.

The display order setting unit 31 presents such visual target imagescorresponding to a plurality of the visual function test items, forexample, so that the respective visual function test items can beperformed, for example, in an order programmed in advance. Moreover, thevisual target images of the respective visual function test items are ina display state, which corresponds to the viewing angle, the visualacuity and the parallax, which are set previously by the observer, andis set by the visual target image selection presentation unit 20.

In the visual function testing device, in accordance with the displayorder set by the display order setting unit 31, the display ordersetting unit 31 calls out the visual target images stored in the visualtarget image storage unit 29, and the visual target images are renderedby the visual target image rendering unit 13. In such a way, the visualfunction testing device can program a testing order of the plurality oftest items, and can mount a function capable of implementing a screeningtest for a plurality of visual functions in a short time. Hence, forexample, when the visual function is desired to be tested after acontent video such as a movie is seen by using the visual target imagepresentation unit 2, then the screening test is only started, wherebythe visual target images of the plurality of visual function test itemscan be presented, and the visual function tests can be implemented.

Tenth Embodiment

Next, a description is made of a visual function testing deviceaccording to a tenth embodiment. Note that the same reference numeralsare assigned to similar portions to those of the above-mentionedembodiments, whereby a detailed description thereof is omitted.

As shown in FIG. 23, this visual function testing device includes a testresult output unit 32, which outputs test results of the visual functiontests selected by the visual function test item selection unit 11, inaddition to the constituents of the visual function testing devices ofthe above-mentioned embodiments. This test result output unit 32 outputsthe test results, which correspond to the respective visual functiontest items which can be performed by the visual function test device, ina predetermined format. This predetermined format is a format in whichtest results of the plurality of visual function test items matched withthe preset current test contents can be seen on a printing sheet.

For example, as in the visual function testing device shown as the ninthembodiment, the visual function testing device as described above canpresent the visual target images of the plurality of visual functiontest items in a predetermined order, and can output the test results ofthe visual function test items in response to an operation of theobserver. In such a way, even if the observer does not have technicalknowledge about the visual function tests, the visual function testingdevice can draw results of the visual function test results from outputresults of the test result output unit 32.

Note that the above-mentioned embodiments are merely examples of thepresent subject matter. Therefore, it is a matter of course that thepresent subject matter is not limited to the above-mentionedembodiments, and that a variety of modifications are possible inresponse to the design and the like within the scope without departingfrom the technical sprit according to the present subject matter even ifsuch modifications are out of the embodiments described above.

INDUSTRIAL APPLICABILITY

In accordance with the present disclosure, it will be industriallyapplicable to manufacture a visual function testing device that performsthe plurality of visual function tests by itself.

REFERENCE SIGNS LIST

-   1 CONTROL DEVICE-   2 VISUAL TARGET IMAGE PRESENTATION UNIT-   11 VISUAL FUNCTION TEST ITEM SELECTION UNIT-   12 VISUAL TARGET IMAGE GENERATION UNIT-   13 VISUAL TARGET IMAGE RENDERING UNIT-   14 VIEWPOINT DISTANCE INPUT UNIT-   15 VISUAL ANGLE INPUT UNIT-   20 VISUAL TARGET IMAGE SELECTION PRESENTATION UNIT-   21 VISUAL TARGET IMAGE OPERATION UNIT-   22 VISUAL TARGET IMAGE ADJUSTMENT UNIT-   23 VIEWPOINT DISTANCE CALCULATION UNIT-   24 VIEWING ANGLE INPUT UNIT-   25 VISUAL ACUITY INPUT UNIT-   26 PARALLAX INPUT UNIT-   27 VIEWPOINT DISTANCE MEASUREMENT UNIT-   28 VISUAL TARGET IMAGE SELECTION STORAGE UNIT-   29 VISUAL TARGET IMAGE STORAGE UNIT-   30 DISPLAY SETTING STORAGE UNIT-   31 DISPLAY ORDER SETTING UNIT-   32 TEST RESULT OUTPUT UNIT

We claim:
 1. A device comprising: a display for displaying a visualtarget for testing a visual function; a memory storing a program; and aprocessor; wherein the program, when executed by the processor, causesthe processor to determine a size of the visual target and a positionwhere the visual target is displayed on the display, based on a distancebetween an examinee and the display, and display the visual target withthe determined size at the determined position on the display.
 2. Thedevice according to claim 1, wherein, the program causes the processorto determine the size of the visual target and the position where thevisual target is displayed on the display, and display the visual targetwith the determined size at the determined position on the display,corresponding to at least one of a visual acuity test, a visual fieldtest, a stereopsis test, a binocular vision test, and an eye positiontest.
 3. The device according to claim 1, wherein, the program causesthe processor to determine the size of the visual target and theposition where the visual target is displayed on the display for each ofa right eye and left eye of the examinee, and display the visual targetwith the determined size at the determined position on the display foreach of the right eye and left eye of the examinee, corresponding to thestereopsis test.